That's a bizarre suggestion for this country, which is infamous for its willingness to just let market forces work things out.
No, instead, we should just tax the heck out of gasoline and let people decide how fast they can afford to go...if they can afford to go at all.
Or better yet, let's take those tax revenues and actually invest in public transportation infrastructure. If we also reward good local development decisions, people might not require a car for 99.99% of their trips. And that would be the best situation by far.
BTW, here's a nifty Department of Energy report from April, 2008 on gasoline usage trends chock-a-block full of graphs, charts, and other statistical goodness. Enjoy!